System and method for igniting a combustor

ABSTRACT

An ignition system for a combustor includes an access port through a wall of the combustor and a laser outside the combustor and aligned with the access port to generate a beam along a path. A lens in the path of the beam focuses the beam at a focal point inside the combustor, and a shutter has a first position in the path and a second position out of the path. A method for igniting a combustor includes generating a beam along a path, focusing the beam to a focal point inside the combustor, and moving a shutter from a first position in the path to a second position outside of the path.

FIELD OF THE INVENTION

The present invention generally involves a system and method for igniting a combustor. In particular embodiments, the system and method may employ a laser to provide a focused beam for igniting a fuel in the combustor.

BACKGROUND OF THE INVENTION

Combustors are known in the art for igniting fuel with air to produce combustion gases having a high temperature and pressure. For example, gas turbine systems, aircraft engines, and numerous other combustion-based systems include one or more combustors that mix a working fluid such as air with fuel and ignite the mixture to produce high temperature and pressure combustion gases. Each combustor generally includes an igniter to initiate the combustion which then becomes self-sustaining. In addition, the igniter may be used to re-initiate the combustion when needed. For example, gas turbine systems having multiple combustors may occasionally experience an interruption in combustion in a single combustor which, if not promptly re-ignited, may result in an unanticipated or unscheduled shut down of the gas turbine system. Similarly, aircraft engines occasionally operate under conditions known to create instabilities in the normally self-sustaining combustion and therefore may use an igniter that can quickly and reliably re-initiate combustion when needed.

Various systems are known in the art for igniting combustors. For example, conventional igniters often include a sparkplug that provides a spark inside the combustor to ignite the fuel and air mixture. To effectively operate, the spark produced by the sparkplug must be close enough to the fuel to ignite the fuel. This generally requires either inserting the sparkplug into the combustion chamber to reach the fuel spray or increasing the width of the fuel spray to reach the sparkplug. Inserting the sparkplug into the combustor may interfere with the flow of fuel, air, and combustion gases in the combustor, and increasing the width of the fuel spray to reach the sparkplug may reduce the efficiency of the combustor once combustion is initiated and self-sustaining. Extending the sparkplug into the combustor to initiate combustion and retracting the sparkplug once combustion has been initiated is a useful solution. However, the sparkplug may become inoperable in the event the mechanism for extending and retracting the sparkplug malfunctions.

More recent attempts have been made to incorporate a laser as an ignition source. The laser may be located outside of the combustor and still generate a laser beam having a focal point in the path of a more narrow fuel spray inside the combustor. A window or lens between the laser and the focal point provides a shutter between the combustion gases and the laser to protect the focal lens. However, foreign object debris, oil, fuel, combustion gases, and other contaminants tend to foul the window or lens over time. As the window or lens becomes fouled, the window or lens may refract or distort the laser beam. The refraction or distortion of the laser beam may move the focal point of the laser beam so that the focal point of the laser beam is no longer coincident with the narrow fuel spray, rendering the igniter inoperable. Moreover, the new focal point of the laser beam may result in damage to the combustor and/or the laser. Material fouling of the lens surface can produce rapid heating of the lens surface as a result of absorption of the laser energy by the fouling material. A rapid temperature change at the lens surface can result in permanent degradation or failure of the lens. As a result, an improved system and method for igniting a combustor would be useful.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.

One embodiment of the present invention is an ignition system for a combustor. The system includes an access port through a wall of the combustor and a laser outside the combustor and aligned with the access port to generate a beam along a path. A lens in the path of the beam focuses the beam at a focal point inside the combustor, and a shutter has a first position in the path and a second position out of the path.

Another embodiment of the present invention is an ignition system for a combustor. The system includes an access port through a wall of the combustor and a laser outside the combustor and aligned with the access port to generate a beam along a path. A fiber-optic bundle in the path focuses the beam at a focal point inside the combustor.

The present invention may also include a method for igniting a combustor. The method includes generating a beam along a path, focusing the beam to a focal point inside the combustor, and moving a shutter from a first position in the path to a second position outside of the path.

Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:

FIG. 1 is a simplified diagram of a system for igniting a combustor according to one embodiment of the present invention;

FIG. 2 is a simplified diagram of a portion of a system for igniting a combustor according to a second embodiment of the present invention;

FIG. 3 is a simplified diagram of the system shown in FIG. 2 with the shutter open;

FIG. 4 is a simplified diagram of a portion of a system for igniting a combustor according to a third embodiment of the present invention; and

FIG. 5 is a simplified diagram of the system shown in FIG. 4 with the shutter open.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention.

Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

Embodiments within the scope of the present invention provide a system and method for igniting a combustor using a laser as the ignition source. The system and method include multiple features that enhance the ability of the laser to effectively and reliably provide an ignition source to the combustor. The system and method may be used with any combustor, including combustors incorporated into gas turbines, aircraft engines, and reciprocating engines.

FIG. 1 shows a simplified diagram of a system 10 for igniting a combustor 12 according to one embodiment of the present invention. The combustor 12 generally includes a combustion chamber 14 with one or more nozzles 16 that supply fuel 18 to the combustion chamber 14. The fuel 18 mixes with air or another working fluid 20 in the combustion chamber 14 and the mixture ignites to produce combustion gases 22 having a high temperature and pressure.

The system 10 generally includes an access port 24 and a laser 26. The laser is located outside of the combustor 12 and aligned with the access port 24 to generate a beam 28 along a path. The beam 28 has a focal point 30 inside the combustor 12 that is generally coincident with the spray of fuel 18 from the nozzles 16. The access port 24 may comprise any suitable opening that allows the passage of light through a wall 32 of the combustor 12. For example, as shown in FIG. 1, the access port 24 may be located on a sidewall 26 of the combustor 12 so that the path of the beam 28 generated by the laser 26 is across the direction of and/or substantially perpendicular to fluid flow through the combustor 12. In this location, the access port 24 may occupy an existing opening in the sidewall 26 of the combustor 12 that is no longer needed. For example, the system 10 may be installed so that the access port 24 occupies the opening previously used by crossfire tubes that are no longer necessary for ignition in gas turbine combustors. Alternately, the access port 24 may be located on the same wall 26 as the nozzle 16 so that the path of the beam 28 generated by the laser 26 is in the same direction as and/or substantially parallel to fluid flow through the combustor 12. In this location, it is believed that a greater variation in the precise location of the focal point 30 may be acceptable and still result in the focal point 30 being generally coincident with the spray of fuel 18 from the nozzle 16.

The laser 26 may comprise any suitable laser known in the art for generating a high intensity and focused beam of energy capable of igniting the fuel 18 in the combustor 12. The laser 26 generally comprises a power supply 34, an optical tube 36, a lens 38, and a shutter 40. One or more of these components may be protected by or enclosed within a container 42 proximate to the access port 24. The shutter 40 may be configured to isolate the container 42 from the combustor 12 so the container 42 does not have to withstand the anticipated temperatures and pressures inside the combustion chamber 14. Alternately, the shutter 40 may be movable, and the container 42 may be configured to continuously or intermittently withstand the anticipated temperatures and pressures inside the combustion chamber 14.

The power supply 34 provides sufficient energy for the laser 26 to generate the beam 28. For example, the power supply 34 may provide sufficient power to allow the laser 26 to generate a focused beam 28 on the order of approximately 1 GW/cm², although the size and capacity of the power supply 34 is not a limitation of the present invention unless specifically recited in the claims. The optical tube 36 connects the laser 26 to the access port 24 and provides an optical path for the beam 28 outside of the combustor 12. As a result, the laser 28 and/or the power supply 34 may be located proximate to or remote from the combustor 12, for example, to facilitate maintenance and replacement of the laser 28 and power supply 34.

FIGS. 2, 3, 4, and 5 provide simplified diagrams of a portion of the system according to alternate embodiments of the present invention. As shown, the lens 38 is generally located in the path of the beam 28 to focus the beam 28 at the focal point 30 inside the combustor 12. The lens 38 may comprise one or more spherical disks to focus the beam 28 at the focal point 30 inside the combustor 12, as shown in FIGS. 2 and 3. Alternately, the lens 38 may comprise a fiber-optic bundle 44 of individual fibers. Each fiber is generally shaped so that the collective fiber-optic bundle 44 focuses the beam 28 at the focal point 30 inside the combustor 12, as shown in FIGS. 4 and 5. The number of fibers included in the fiber-optic bundle 44 may be selected to enhance the reliability of the laser 26. Specifically, the number of individual fibers may be selected so that the laser 26 will continue to operate adequately in the event that individual fibers in the fiber-optic bundle 44 are damaged or occluded by contaminants.

The shutter 40 protects the lens 38 and/or other components inside the container 42 from contaminants inside the combustion chamber 14. To protect the lens 38 and/or other components inside the container 42, the shutter 40 may be generally located anywhere between the lens 38 and the focal point 30, such as in, along, or adjacent to the path of the beam 28 and/or proximate to or inside the access port 24, although the specific location of the shutter 40 is not a limitation of the present invention unless specifically recited in the claims. If located proximate to or inside the access port 24, a seal 46, wiper 48, gasket, or similar insulating material may be connected to or in contact with the shutter 40 to provide a temperature and/or pressure barrier between the combustion chamber 14 and the inside of the container 42.

In various embodiments, the shutter 40 may be substantially transparent to or substantially opaque to the beam 28 and may include coatings on one or both sides of the shutter 40 to reduce or prevent contaminants from the combustion chamber 14 from adhering to the shutter 40. As used herein, “substantially transparent to the beam 28” means that at least a portion of the beam 28 passes through the shutter 40 without significant refraction and/or blockage. A substantially transparent shutter 40 may comprise, for example, quartz, sapphire, transparent glass, tempered glass, acrylics, and other suitable transparent materials known to one of ordinary skill in the art. If substantially transparent to the beam 28, the shutter 40 may remain in the path of the beam 28 during operation of the laser 26, allowing at least a portion of the beam 28 to pass substantially unchanged through the shutter 40. It is believed that the beam 28 may be sufficiently focused as it passes through the shutter 40 to oblate small amount of contaminants that adhere to the shutter 40. It is further anticipated that larger amounts of contaminants that adhere to the shutter 40 will absorb sufficient energy from the beam 28 to melt a hole through the shutter 40, thus allowing the laser 26 to continue to operate until the shutter 40 may be repaired or replaced. As used herein, “substantially opaque to the beam 28” means that the barrier 40 blocks or refracts substantially all of the beam 28, preventing at least a majority of the beam 28 from passing through the shutter 40. A substantially opaque shutter 40 may comprise, for example, opaque glass, opaque tempered glass, opaque acrylics, magnesium oxide pressed powder, or other suitable opaque materials known to one of ordinary skill in the art.

Regardless of whether the shutter 40 is substantially transparent to or substantially opaque to the laser beam 28, the shutter 40 may have a first or closed position in the path of the beam 28 and a second or open position out of the path of the beam 28. In the first position, the shutter 40 is generally between the combustion chamber 14 and the lens 38 to enhance protection to the lens 38 and/or other components inside the container 42, as shown in FIGS. 2 and 4. The laser 26 may be operated with the shutter 40 in the first position, for example, when the shutter 40 is substantially transparent to the beam 28. In the second position, the shutter 40 is out of the path of the beam 28 to allow the beam 28 to freely pass through the access port 24 into the combustion chamber 14, as shown in FIGS. 3 and 5. The laser 26 may be operated with the shutter 40 in the second position, for example, when the shutter 40 is substantially transparent to the beam 28 and partially or fully occluded by contaminants from the combustion chamber 14 or when the shutter 40 is substantially opaque to the beam 28. Movement of the shutter 40 between the first and second positions may allow the wiper 48, if present, to sweep across one or both surfaces of the shutter 40 to reduce or remove contaminants on the shutter 40.

As shown in FIGS. 1-5, the system 10 may further include means for moving the shutter 40 between the first position and the second positions. For example, as shown in FIG. 1, the means may comprise a telescoping member 50 connected to the shutter 40. A fluid 52 may be alternately supplied or vented from the telescoping member 50 to cause the telescoping member 50 to extend or retract, respectively, thus moving the shutter 40 between the first position and the second position. Alternately, as shown in FIGS. 2 and 3, the means may comprise a lever 54 passing through a pivot point 56 and connected to the shutter 40. A hydraulic, pneumatic, or mechanical actuator (not shown) may be configured with the lever 54 to reposition the lever 54, thus moving the shutter 40 between the first position and the second position. FIGS. 4 and 5 provide yet another example of suitable structure for the means for moving the shutter 40 between the first position and the second position. As shown in FIGS. 4 and 5, the means may comprise a servomotor 60 configured to rotate a pin 62 connected to the shutter 40. Rotation of the pin 62 thus causes the shutter 40 to rotate about the pin 62 between the first and second positions. In alternate embodiments, the means for moving the shutter 40 between the first position and the second positions may comprise a threaded engagement, a ratchet and pawl assembly, and/or virtually any pneumatic, hydraulic, and/or mechanical structures known to one of ordinary skill in the art for moving one component with respect to another.

As further shown in FIGS. 2-5, a bias member 58, such as a spring, weight, piston, or similar device, may be connected to the shutter 40 to bias the shutter 40 to one of the first or second positions. For example, the bias member 58 may be attached to the shutter 40 to bias the shutter 40 to the second position so that, in the event the means for moving the shutter 40 between the first position and the second position fails, the bias member 58 may automatically move the shutter 40 to the second position, thus allowing the laser 26 to remain operable until the means for moving the shutter 40 may be repaired or replaced.

As shown in FIGS. 2-5, the system 10 may further include means for sensing a condition of the shutter 40. The condition of the shutter 40 may include, for example, the position of the shutter 40 and/or the amount and/or location of contaminants on the shutter 40. The means may comprise, for example, a light sensor or a temperature sensor, such as a photocell, a photo resistor, a temperature detector, or equivalent structure to detect light or heat passing through or reflected off of the shutter 40. For example, as shown in the figures, a sensor 64 may be located in the container 42 to detect light or heat passing through or reflected off of the shutter 40. The amount of light or heat passing through or reflected off of the shutter 40 may be used to determine the position of the shutter 40 to prevent the inadvertent operation of the laser 26 with the shutter 40 closed. Alternately, or in addition, the amount of light or heat passing through or reflected off of the shutter 40 may indicate the presence, location, and/or amount of contaminants on the shutter 40 to facilitate the scheduling of maintenance or repairs to the laser 26.

The systems 10 described and illustrated in the figures may further provide a method for igniting the combustor 12 that includes generating the beam 28 along a path and focusing the beam 28 to the focal point 30 inside the combustor 12. The method may further include moving the shutter 40 from the first position in the path to the second position outside of the path. In particular embodiments, the method may further include focusing the beam 28 within the fiber-optic bundle 44, moving the shutter 40 from the second position to the first position, and/or sensing the condition of the shutter 40.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other and examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

1. An ignition system for a combustor comprising: a. an access port through a wall of the combustor; b. a laser outside the combustor and aligned with said access port, wherein said laser generates a beam along a path; c. a lens in said path of said beam, wherein said lens focuses said beam at a focal point inside the combustor; and d. a shutter having a first position in said path and a second position out of said path.
 2. The system as in claim 1, wherein said lens comprises a fiber-optic bundle.
 3. The system as in claim 1, further comprising means for moving said shutter between said first position and said second position.
 4. The system as in claim 1, wherein said path of said beam in the combustor is substantially perpendicular to fluid flow through the combustor.
 5. The system as in claim 1, wherein said shutter is substantially transparent to said beam.
 6. The system as in claim 1, further comprising a wiper in contact with said shutter.
 7. The system as in claim 1, further comprising a bias member operatively connected to said shutter to bias said shutter to said second position.
 8. The system as in claim 1, further comprising means for sensing a condition of said shutter.
 9. An ignition system for a combustor comprising: a. an access port through a wall of the combustor; b. a laser outside the combustor and aligned with said access port, wherein said laser generates a beam along a path; and c. a fiber-optic bundle in said path, wherein said fiber-optic bundle focuses said beam at a focal point inside the combustor.
 10. The system as in claim 9, wherein said path of said beam in the combustor is substantially perpendicular to fluid flow through the combustor.
 11. The system as in claim 9, further comprising a shutter having a first position in said path and a second position out of said path.
 12. The system as in claim 11, further comprising means for moving said shutter between said first position and said second position.
 13. The system as in claim 11, wherein said shutter is substantially transparent to the said beam.
 14. The system as in claim 11, further comprising a wiper in contact with said shutter.
 15. The system as in claim 11, further comprising a bias member operatively connected to said shutter to bias said shutter to said second position.
 16. The system as in claim 11, further comprising means for sensing a condition of said shutter.
 17. A method for igniting a combustor comprising: a. generating a beam along a path; b. focusing said beam to a focal point inside the combustor; and c. moving a shutter from a first position in said path to a second position outside of said path.
 18. The method as in claim 17, further comprising focusing said beam with a fiber-optic bundle.
 19. The method as in claim 17, further comprising moving said shutter from said second position to said first position.
 20. The method as in claim 17, further comprising sensing a condition of said shutter. 